A hard disk drive typically contains one or more disks clamped to a rotating spindle, at least one head for reading data from and/or writing data to the surfaces of each disk, and an actuator utilizing linear or rotary motion for positioning the head(s) over selected data tracks on the disk(s). A rotary actuator is a complex assembly that couples a slider on which a head is attached or integrally formed to a pivot point that allows the head to sweep across a surface of a rotating disk. A servo system uses positioning data read by the head from the disk to determine the position of the head on the disk. In common servo schemes, positioning data can be included in servo wedges, each comprising servo patterns. Servo wedges can be written to each disk using a media writer, prior to assembly of the hard disk drive. Alternatively, a reference surface of one disk can be used to write servo wedges on blanks disks substituted for media-written disks in an assembled hard disk drive.
The reference surface can include a template pattern containing information for writing servo patterns on the surfaces of the disks. The template pattern typically includes timing bursts, or pulses, defining information. Chevrons can be incorporated into template patterns to indicate radial positioning of the head. The maximum frequency of the template pattern can be constrained by a combination of factors, including the minimum available feature-size of the pattern elements, the angle of the chevrons and an orientation of the head at the inner diameter of the disk. A low frequency template pattern mayn introduce more written-in runout when writing servo patterns than a template pattern having a higher frequency. The performance of a hard disk drive can be adversely affected by an increased amount of written-in runout contained in a servo pattern.